Heat transfer arrangement

ABSTRACT

A heat transfer arrangement for heating a working fluid by means of a flowing hot fluid comprises a fluid channel for carrying the flowing hot fluid, a pipe bundle arranged in the fluid channel for carrying the working fluid, wherein the pipe bundle comprises a number of pipeline segments running parallel to each other in a longitudinal direction and a carrying structure permanently connected to the fluid channel for holding the pipe bundle in the fluid channel. The pipeline segments are each supported on the carrying structure on at least a first non-moving bearing point and on at least a second bearing point separated from the first bearing point in the longitudinal direction and having clearance movement in at least one direction.

The present invention relates to a heat transfer arrangement for heating, in particular for vaporizing and superheating, a working fluid by means of a flowing hot fluid, in particular by means of an exhaust gas flow of an internal combustion engine, having a fluid passage for conducting the flowing hot fluid, having a bundle of tubes arranged in the fluid passage for conducting the working fluid, with the bundle of tubes comprising a plurality of piping sections extending in parallel to one another along a longitudinal direction, and having a support structure fixedly connected to the fluid passage for holding the bundle of tubes in the fluid passage.

Such apparatus are also called “heat exchangers” and are used in different kinds of utilization of waste heat carried by the hot fluid. For example, such heat exchangers can be used for exhaust gas utilization in internal combustion engines in that some of the thermal energy of the hot exhaust gas flow is converted into technically usable mechanical energy, for example within the framework of a closed vapor circuit. Fuel can ultimately hereby be saved. The piping sections of the bundle of tubes which extend in parallel, and are in particular in straight lines, are flowed around by the hot fluid, with an effective heat transfer to the working fluid located in the interior of the piping sections taking place. The bundle of tubes can in principle be arranged at any desired point in an exhaust gas line, for example in a muffler housing.

The fastening of the bundle of tubes in the fluid passage is problematic in that thermal expansions and mechanical stresses occur during operation which can result in a critical material load on the piping sections.

It is therefore an object of the invention to make possible a secure fastening of heat exchangers in a tube bundle construction at the associated fluid passage with simple construction means.

The object is satisfied by a heat transfer arrangement having the features of claim 1.

In accordance with the invention, the pipeline sections are each immovably supported at the support structure at at least one first support point and are supported at the support structure at at least one second support point spaced apart therefrom in the longitudinal direction and having movement clearance in at least one direction. The bundle of tubes is therefore supported at least twice, with one bearing being configured as a locating bearing and at least one bearing remote therefrom being configured as a floating bearing. A secure fastening of the piping sections among one another and of the bundle of tubes within the fluid passage is thus ensured, on the one hand. On the other hand, the floating bearing allows compensation movements of the piping sections as a result of thermal expansion or mechanical stresses so that unwanted tensions or material overloads are avoided.

Further developments of the invention are set forth in the dependent claims, in the description and in the enclosed drawings.

In accordance with an embodiment, the movement clearance at the second support point is in the longitudinal direction, preferably exclusively. The thermal expansions and contractions of the pipeline sections which frequently occur in the axial direction during operation can thus be compensated.

In accordance with a further embodiment of the invention, all the first and/or all the second support points are in a transverse plane respectively extending at a right angle to the longitudinal direction. All the pipeline sections of the bundle of tubes are thus evenly supported at two points.

The support structure can comprise a first support element for providing all the first support points and a second support element separate from the first support element for providing all the second support points. This allows the provision of a free space which is located between the two separate support elements and which facilitates a largely unimpeded throughflow of the bundle of tubes.

The support elements are preferably configured as areal and extend in a respective transverse plane extending at a right angle to the longitudinal direction. On an onflow of the bundle of tubes transversely to the longitudinal direction, only a slight resistance is thus opposed to the hot fluid flow.

The support structure preferably comprises at least one, preferably two arrangements of stacked elongate spacers which are each arranged transversely to the longitudinal direction and in which cut-outs are provided for leading through piping sections disposed next to one another. The spacers can be arranged between individual planes of the bundle of tubes and can thus stabilize and hold the bundle overall.

In accordance with a preferred embodiment of the invention, means are provided for tensioning the stacked spacers with respect to one another. A fixing of all piping sections of the bundle of tubes takes place by the tensioning of the spacers with respect to one another, with it depending on the dimensioning of the cut-outs whether a movement clearance for the piping sections is present in the tensioned state, that is whether a locating bearing or a floating bearing is established.

Two clamps can be provided for tensioning the stacked spacers the clamps being arranged above and below the bundle of tubes and including the arrangement of spacers. This allows a particularly simple construction.

The clamps can be movable toward one another by means of a screw connection, in particular by means of an arranged of threaded bars and nuts. The clamps can thus be moved toward one another by tightening the nuts, with the spacers located between the clamps being pressed together and the bundle of tubes being fixed. An arrangement of threaded bars and associated nuts in particular minimizes the manufacturing effort for the tensioning.

In accordance with an embodiment of the invention, the clamps are connected to one another, in particular welded to one another, in the tensioned state by means of a rigid bridging element. The screw connection can be dispensed with in this embodiment.

The spacers can furthermore be fixed relative to one another by at least one U-shaped section rail. Such a section rail can prevent an unwanted slipping of the spacers before or during the tensioning.

In accordance with a further embodiment of the invention, flow guide walls are arranged at both sides of the bundle of tubes in the fluid passage. Such flow guide walls can improve the efficiency of the heat exchanger in that they directly conduct the hot fluid flow between the individual piping sections. The flow guide walls can preferably be provided with beads to further reduce the flow of hot fluid flowing by at the side of the bundle of tubes.

The invention also relates to a heat engine having a heat transfer arrangement in accordance with one of the above embodiments, having an expansion machine and having a condenser for cooling the working fluid, with the working fluid being conducted in a cycle, in particular in a Rankine cycle, through the heat transfer arrangement, the expansion machine and the condenser. The heat transfer arrangement can thus so-to-say work both as a vaporizer and as a super heater, with the working fluid being heated, vaporized and superheated with the aid of the thermal energy of the hot fluid. The thermal energy thereby stored in the working fluid is converted into technically usable mechanical energy in the expansion machine. The working fluid is subsequently recondensed in the condenser, recooled and finally again supplied to the heat transfer arrangement.

The invention further relates to an exhaust gas system for an internal combustion engine into which a heat transfer arrangement as described above is integrated.

The invention will be described in the following by way of example with reference to the drawings.

FIG. 1 shows a perspective view of a heat transfer arrangement in accordance with a first embodiment of the invention;

FIG. 2 shows a heat transfer arrangement in accordance with a second embodiment of the invention; and

FIG. 3 shows a heat transfer arrangement in accordance with a third embodiment of the invention.

In accordance with FIG. 1, a heat exchanger comprises a bundle of tubes 11 which in the present embodiment is composed of twenty-four tube coils arranged next to one another and fed individually with a working fluid. Each tube coil 12 comprises a plurality of straight piping sections 13 which are arranged above one another, which extend in parallel to one another, which each extend in parallel to a longitudinal direction L and which are connected by means of slanted U-shaped bends 14. The bundle of tubes 11 is configured for assembly in a fluid passage, not shown, for example in a muffler housing of an exhaust gas train. The hot exhaust gas flows along a main direction of flow S through the fluid passage and impacts the arrangement of piping sections 13. An effective heat transfer hereby takes place from the hot exhaust gas to the working fluid conducted in the tube coils 12. The working fluid can be vaporized and superheated in this manner so that it can subsequently perform mechanical work in an expansion machine. The working fluid is subsequently condensed, recooled and again supplied to the bundle of tubes 11.

The fastening of the bundle of tubes 11 in the fluid passage takes place by means of a support structure 15 which comprises two holding rings 15 a, 15 b separated from one another. The holding rings 15 a, 15 b are configured as areal and extend in a respective transverse plane extending at a right angle to the longitudinal direction L. In this manner, the flow of the exhaust gas is only minimally impeded along the main direction of flow S. The outer extent of the holding rings 15 a, 15 b is configured for a fixed connection to the fluid passage and is especially adapted to the geometry of the passage wall. An adaptation of the support structure 15 to different construction shapes of fluid passages can thus take place by a simple replacement of the holding rings 15 a, 15 b.

Two oppositely disposed clamps 23 are welded at the flat side to each of the holding rings 15 a, 15 b. Before the welding, the clamps 23 can be moved toward one another by means of two threaded bars 25 and associated nuts 37. An arrangement of stacked elongate spacer rails 19 is located between the two clamps 23 and the spacer rails are each led between the horizontal planes of the bundle of tubes 11 and cut-outs 21 are provided in them for leading through the piping sections 13 which are disposed next to one another. U-shaped section rails 29 each engage around the threaded bars 25 and so provide a correct alignment of the spacer rails 19 relative to one another. The spacer rails 19 can be tensioned with respect to one another by tightening the nuts 27, with the piping sections 13 being clamped in the cut-outs 21.

Each piping section 13 is thus received and held relative to the support structure 15 at a first support point 17 a and at a second support point 17 b spaced apart therefrom in the longitudinal direction L. In this respect, the extent of the clamping of the piping sections 13 in the cut-outs is selected such that each piping section 13 is held immovably at the first support part 17 a, whereas a certain movement clearance is present in the axial direction, that is in the longitudinal direction L, at the second support point 17 b. All the first support points 17 a in this respect lie in the transverse plane defined by the holding ring 15 a disposed at the left in the drawing, whereas all the second support points 17 b lie in the transverse plane defined by the holding ring 15 b disposed at the right. On a fastening of the support structure 15 in a fluid passage, a secure support of the bundle of tubes 11 is thus ensured at two spaced apart points, whereas simultaneously compensation movements of the piping sections 13 are always possible.

A further embodiment of a heat exchanger in accordance with the invention is shown in FIG. 2, with this embodiment having the same design in principle as the arrangement in accordance with FIG. 1. In addition, however, flow guide walls 30 are provided at both sides of the bundle of tubes 11 in order better to conduct the hot exhaust gas flow through the bundle of tubes 11. Beads 31 provided in the flow guide walls 30 each project into the intermediate spaces between adjacent tube coils 12 and thus reduce an unwanted flowing past of the exhaust gas at the side.

FIG. 3 shows a further embodiment of a heat exchanger in accordance with the invention, with here, instead of the screw connection formed by threaded bars 25 and nuts 27, the U-shaped section rails 29 themselves being welded to the clamps 23 and, optionally, with the spacer rails 19. The respective arrangement of clamps 23, spacer rails 19 and section rails 29 is preloaded in a suitable clamping apparatus for this purpose and is welded in the clamped state. The connection of the section rails 29 to the spacer rails 19 can in this respect take place point by point or over a full area.

It is understood that the principle of the double support with a movement possibility can be applied to a plurality of different types of flow conduction, with it in particular not being important whether the individual straight piping sections 13 are connected to one another in parallel, in series or in a combined manner.

Reference Numeral List

-   11 bundle of tubes -   12 tube coil -   13 piping section -   14 bend -   15 support structure -   15 a, 15 b holding ring -   17 a first support point -   17 b second support point -   19 spacer rail -   21 cut-out -   23 clamp -   25 threaded bar -   27 nut -   29 section rail -   30 flow guide wall -   31 bead -   L longitudinal direction -   S main direction of flow 

1-14. (canceled)
 15. A heat transfer arrangement for heating a working fluid by means of a flowing hot fluid, comprising a fluid passage for conducting the flowing hot fluid; a bundle of tubes (11) for conducting the working fluid and arranged in the fluid passage, with the bundle of tubes comprising a plurality of piping sections (13) extending in parallel to one another along a longitudinal direction (L); and a support structure (15) fixedly connected to the fluid passage for holding the bundle of tubes (11) in the fluid passage, wherein the piping sections (13) are each supported immovably at the support structure (15) at at least one first support point (17 a) and are supported at the support structure (15) at at least one second support point (17 b) spaced apart therefrom in the longitudinal direction (L) with movement clearance in at least one direction.
 16. The heat transfer arrangement in accordance with claim 15, wherein the movement clearance at the second support point (17 b) is in the longitudinal direction (L).
 17. The heat transfer arrangement in accordance with claim 15, wherein the movement clearance at the second support point (17 b) is exclusively in the longitudinal direction (L).
 18. The heat transfer arrangement in accordance with claim 15, wherein one of at least all of the first and all of the second support points (17 a, 17 b) is/are disposed in a transverse plane respectively extending at a right angle to the longitudinal direction (L).
 19. The heat transfer arrangement in accordance with claim 15, wherein the support structure (15) comprises a first support element (15 a) for providing all the first support points (17 a) and a second support element (15 b) separate from the first support element (15 a) for providing all the second support points (17 b).
 20. The heat transfer arrangement in accordance with claim 19, wherein the support elements (15 a, 15 b) are configured as areal and respectively extend in a transverse plane extending at a right angle to the longitudinal direction (L).
 21. The heat transfer arrangement in accordance with claim 15, wherein the support structure (15) comprises at least one arrangement of stacked elongate spacers (19) which are each arranged transversely to the longitudinal direction (L) and in which cut-outs (21) are provided for leading through piping sections (13) disposed next to one another.
 22. The heat transfer arrangement in accordance with claim 21, wherein the support structure (15) comprises two arrangements of stacked elongate spacers (19).
 23. The heat transfer arrangement in accordance with claim 21, wherein means (23, 25, 27, 29) are provided for tensioning the stacked spacers (19) with respect to one another.
 24. The heat transfer arrangement in accordance with claim 23, further comprising two clamps (23) for tensioning the stacked spacers (19), the clamps being arranged above and below the bundle of tubes (11) and including the arrangement of spacers (19).
 25. The heat transfer arrangement in accordance with claim 24, wherein the clamps (23) can be moved toward one another by means of a screw connection (25, 27).
 26. The heat transfer arrangement in accordance with claim 25, wherein the clamps (23) can be moved toward one another by means of threaded bars (25) and nuts (27).
 27. The heat transfer arrangement in accordance with claim 25, wherein the clamps (23) are connected to one another by means of a rigid bridging element (29) in the tensioned state.
 28. The heat transfer arrangement in accordance with claim 27, wherein the clamps (23) are welded to one another.
 29. The heat transfer arrangement in accordance with claim 21, wherein the spacers (19) are fixed relative to one another by at least one U-shaped section rail (29).
 30. A heat transfer arrangement in accordance with claim 15, further comprising flow guide walls (30), the flow guide walls being arranged at both sides of the bundle of tubes (11) in the fluid passage.
 31. A heat machine, having a heat transfer arrangement comprising a fluid passage for conducting the flowing hot fluid; a bundle of tubes (11) for conducting the working fluid and arranged in the fluid passage, with the bundle of tubes comprising a plurality of piping sections (13) extending in parallel to one another along a longitudinal direction (L); and a support structure (15) fixedly connected to the fluid passage for holding the bundle of tubes (11) in the fluid passage, wherein the piping sections (13) are each supported immovably at the support structure (15) at at least one first support point (17 a) and are supported at the support structure (15) at at least one second support point (17 b) spaced apart therefrom in the longitudinal direction (L) with movement clearance in at least one direction, the heat machine having an expansion machine and having a condenser for cooling the working fluid, wherein the working fluid is conducted in a cycle through the heat transfer arrangement, the expansion machine and the condenser.
 32. A heat machine in accordance with claim 31, wherein the working fluid is conducted in a Rankine cycle.
 33. An exhaust gas system for an internal combustion engine into which a heat transfer arrangement is integrated, the heat transfer arrangement comprising a fluid passage for conducting the flowing hot fluid; a bundle of tubes (11) for conducting the working fluid and arranged in the fluid passage, with the bundle of tubes comprising a plurality of piping sections (13) extending in parallel to one another along a longitudinal direction (L); and a support structure (15) fixedly connected to the fluid passage for holding the bundle of tubes (11) in the fluid passage, wherein the piping sections (13) are each supported immovably at the support structure (15) at at least one first support point (17 a) and are supported at the support structure (15) at at least one second support point (17 b) spaced apart therefrom in the longitudinal direction (L) with movement clearance in at least one direction. 